This invention is in the field of scan converters having TV-type displays, and more particularly in a scan converter system that provides scanned information substantially devoid of flicker.
The prior art systems, typically represented by U.S. Pat. No. 3,864,660 provides a group of consecutively scanned lines are read out followed by a blank space substantially of equal time duration as the read out consecutively scanned lines. Therefore, the first field will comprise say five solid lines and five missing lines in alternate fashion. The five missing lines will read into the blanked area from the second field. Therefore, in prior art systems, groups of visual information are displayed during one time duration repeated at a 30 cycle rate, and such 30 cycle repetition rate is well within the objectionable flicker range.
Another objective is to avoid in prior art systems the change from the read mode to the write mode of an entire large portion of the picture at one time (consisting of 5 to 7 lines at a time), and by so doing the TV screen at that time is blanked out. Such prior art functions and prior art objectives are disclosed in U.S. Pat. No. 3,864,660 wherein the patent specification shows an increase in flicker due to the described functions.